1. Field of the Invention
This invention relates to a sensor for detecting acceleration.
2. Prior Art
Japanese Laid-Open (Kokai) Patent Application No. 109374/88, filed by the Applicant of this application, discloses an acceleration sensor which comprises a tubular casing, a magnetic member in the form of an iron ball received within the casing, a differential transformer (detection member) mounted externally of the casing, and a ring-shaped permanent magnet disposed externally of the differential transformer to attract the iron ball to a central portion of the differential transformer. The casing, the differential transformer and the permanent magnet are mounted within a body immovably relative to the body. The sensor is mounted on an object to be sensed in such a manner that the axis of the casing coincides with the sensing direction.
In the above conventional acceleration sensor, particularly, the relation between the magnetic force of the permanent magnet and the position of the casing, as well as the relation between the magnetic force of the permanent magnet and the position of the differential transformer, is important. However intended functions have not always been achieved due to manufacturing errors of the component parts and an error in magnetization of the permanent magnet.
Japanese Laid-Open Patent Application No. 144261/88 and Japanese Laid-Open Utility Model Application Nos. 97862/88 and 109654/88, filed by the Applicant of this application, also disclose acceleration sensors employing a tubular casing, an iron ball, a permanent magnet and a differential transformer. Based on the above four earlier Japanese applications and other applications, a U. S. patent application was filed on Oct. 23, 1987 under Ser. No. 113,180.
U.S. Pat. Nos. 2,979,959, 4,311,051 and 4,365,513 describe acceleration sensors using an iron ball.
Japanese Laid-Open Patent Application No. 62870/86 discloses a two-dimensional acceleration sensor comprising a pair of permanent magnets disposed respectively on opposite sides of a disc-shaped casing.
Further, U.S. Pat. Nos. 3,100,292 and 4,047,439 and Japanese Laid-Open Patent Application Nos. 203861/85, 233564/85 and 252271/85 disclose acceleration sensors.
However, none of the above-mentioned prior art publications disclose means for adjusting the relative position between the permanent magnet and the casing and the relative position between the permanent magnet and the differential transformer.